1. Field of the Disclosure
The present disclosure relates generally to an electrophotographic photoconductor system for use in an electrophotographic device, and more specifically, to an electrophotographic photoconductor system that includes a charge generation layer capable of absorbing light having a wavelength of about 350 nanometers (nm) to about 850 nm.
2. Description of the Related Art
An electrophotographic device is usually employed to form an image on a media sheet. Suitable examples of the electrophotographic device include laser printer, copying machine, multifunctional peripheral, and the like. Suitable examples of the media sheet include, but are not limited to, textile substrates, non-woven substrates, canvas substrates, and cellulose substrates.
A typical electrophotographic device includes an electrophotographic photoconductor system (hereinafter referred to as a “photoconductor system”) capable of generating latent electrostatic images thereon. The photoconductor system includes an electroconductive support, a charge generation layer disposed onto the electroconductive support, and a charge transport layer disposed on the charge generation layer. Such a photoconductor system may be categorized as a dual-layer negative-charging photoconductor system.
The electroconductive support is capable of providing a conducting support to the photoconductor system. Typically, the electroconductive support is in form of a drum composed of either polymeric materials or metallic materials.
The charge generation layer is capable of generating charge by absorbing light (such as a laser light or light emitted by light emitting diodes). More specifically, the charge generation layer includes a photosensitive material dispersed in a binder, wherein the photosensitive material is capable of generating electron-hole pairs by absorbing the light.
The charge transport layer is capable of transferring the charge generated by the charge generation layer to a surface of the photoconductor system. More specifically, the charge transport layer is composed of one or more charge transport compounds and is capable of transferring either holes or electrons generated by the charge generation layer to the surface of the photoconductor system. For the photoconductor system, which is categorized as the dual-layer negative-charging photoconductor system, the charge transport layer transfers the holes to the surface of the photoconductor system, and the electrons to the electroconductive support.
During a typical image forming process, the photoconductor system is charged to a predetermined voltage. The charging of the photoconductor system makes it sensitive to light. Thereafter, light provided by a light emitting unit, which includes a light source for producing the light of a particular wavelength and a lens for modulating the light, irradiates the surface of the photoconductor system in a predetermined pattern. Usually, such a predetermined pattern is in accordance with the image that is required to be generated onto the surface of the photoconductor system.
The light that irradiates the surface of the photoconductor system is then absorbed by the photoconductor system. More specifically, the charge generation layer of the photoconductor system absorbs photons of the light thereby generating electron-hole pairs therewithin. Thereafter, the charge transport layer transfers the electrons to the electroconductive support and the holes from the charge generation layer to the surface of the photoconductor system.
At the surface of the photoconductor system, the holes dissipate the charge present on particular areas to form a latent electrostatic image thereon. The latent electrostatic image is thereafter toned and the toned image is transferred, either directly or through an intermediate transfer member, and fused onto the media sheet to generate the image.
During the image forming process, light having high wavelength, in the region of about 700 nanometers (nm) to about 800 nm, is usually employed to irradiate the photoconductor system. However, it is highly desirable to employ light having low wavelength, typically in the region of 350 nm to about 500 nm, for providing higher print resolutions during the image forming process. This may be appreciated by considering the following expression for spot diameter, which measures degree of print resolution:d=(π/4)*(λf/D)
In the expression, as stated above, “d” denotes spot diameter of a spot generated at surface of a photoconductor system, “λ” denotes wavelength of light employed for generating the spot, “f” denotes focal length of lens used to modulate the light and “D” denotes diameter of the lens. Therefore, it may be observed that a low wavelength of the light helps forming spots of small diameters, and correspondingly provides a better print resolution.
Further, due to the recent surge in use of high-density storage mediums, such as Digital Video Disc (DVD), the demand for light having a wavelength, such as a wavelength of about 650 nm, has increased tremendously. In addition, due to a high demand of technologies, such as Blu-ray and high-definition technology (HD-DVD), the manufacturing costs associated with Gallium nitride (GaN) laser light and aluminum-gallium-indium-nitride (AlGaInN) laser light (which typically have a wavelength of around 405 nm), have reduced enormously. Such an increased demand of technologies employing light having shorter wavelengths, has spurred the development of photoconductor systems that are capable of absorbing light having a shorter wavelength, such as wavelength ranging from about 350 nm to about 850 nm.
Moreover, in most of conventional photoconductor systems, the charge transport layer begins to absorb light having low wavelength, such as a wavelength ranging from about 350 nm to about 500 nm. More specifically, the charge transport layer absorbs photons of the light having low wavelength, and such a property of the charge transport layer effectively lowers the efficiency of the charge generation layer by lowering photon count at the charge generation layer. Further, it is also observed that an extended exposure of the charge transport layer with light having low wavelength may lead to a gradual photo-induced degradation of the photoconductor system. Therefore, it is important to select a charge transport layer that absorbs negligible amount of radiation when exposed to light having low wavelength.
Therefore, there is a need for developing a photoconductor system that includes a charge generation layer, which exhibits large absorption of light having wavelength of about 350 nm to about 850 nm. Further, the photoconductor system should be capable of producing images with high print resolution when employed in the electrophotographic device.